The Birnboim-Schrag multiple-lumped resonator is being modified for use with dilute aqueous macromolecular solutions. It will be used to study viscoelastic properties of fibrinogen solutions, plasma, and whole blood. The frequency dependence of these properties is related to the length and flexibility of elongated macromolecules. Systems with intermediate fibrin polymers, stabilized by suitable reagents, will be included, and if the prospects appear favorable abnormal plasmas will examined to attempt detection of intermediate polymers or soluble fibrin-fibrinogen complexes. In addition, the modified Birnboim-Ferry transducer apparatus will be used to study viscoelastic properties of fibrin clots. The magnitude and frequency dependence of the storage and loss shear moduli will be measured for clots formed from fibrinogen and from fibrin monomer precursor, both with and without ligation, using both thrombin and ancrod for activation, studying effects of fibrin concentration, pH, ionic strength, and other variables. These measurements are related to the deformability of the three-dimensional network structure and the rates at which linkages can rearrange. Viscoelastic measurements of creep and stress relaxation will also be made.